This invention relates to compressed gas insulated high voltage switching installations in general and, in particular, to such an installation with a single phase metallic encapsulation.
A high voltage switching installation of this general type which includes bus bar systems and switch gear sections, at least one of which is firmly anchored in space, and in which compensators with tie rods are arranged in line with the bus bar systems is described in the journal "Elektrie" 1977, pages 316 to 321 and in particular page 317.
In such compressed gas insulated high voltage switching installation which sometimes can have a large lengthwise dimension, considerable problems arise with respect to the thermal expansion of the housings of the bus bar systems. In order to avoid mechanical stresses in the housings, certain points of the high voltage switching installation are firmly anchored in space and therefore form a fixed point. In the known high voltage switching installation, this fixed point is in the center of a switch gear section which is located at approximately the center of the installation. The parts connected to the fixed point via the housings of the bus bar systems are supported on the foundation so that they can slide and can move as a whole in the event of length changes of the housings due to temperature changes. While additional stresses of the housings forming the encapsulation which occur with unfavorable leverage as referred to the sliding points of the section, are produced in the switchgear sections, compensators with tie rods are also arranged in the train of the bus bar housings. Since the tie rods always bridge the compensator, the compensator can only equalize the dimensional deviations caused by tolerances between the individual switchgear sections.
It is further known (brochure of the firm COQ, C-P-76-E) to build the compensators into the housings of the bus bar in such a way that they take up longitudinal expansion. In view of the gas pressure in the encapsulation tube, the tie rods are arranged in this case between fixed points of the installation in such a manner that they bridge the compensators. However, in this cse, care must be taken that the tie rids are designed out only for the operational gas pressure but, so as to account for the case of a fault arc with a pressure increase to three times the value, for this increased gas pressure. A further problem arises for long tie rods in compressed gas insulated installations if the gas chambers are evacuated in connection with installation or maintenance work, causing a buckling stress to act on the compensator. In addition, the tie rods's own elongation leads to additional loads on the fixed points.
Particularly in hydroelectric power stations with turbine and switching section spacings on the order of 40 to 50 m and bus bar lengths of several hundred meters, the known compensator/tie rod arrangements are applicable only with additional, high cost technical measures. It is an object of the present invention to take up the longitudinal expansion of the housings of the bus bar system, without great cost, through a special mechanical design of such compressed gas insulated encapsulated high voltage switching installations in such a manner that no appreciable mechanical stresses occur in the installation.